By the photo excellent properties, the silver halide light-sensitive material has been used extensively heretofore, and has been utilized extensively in the imaging arts as a material of high quality.
However, in the silver halide light-sensitive material of the conventional art, there are problems in addition to development and fixing process being complex, and for discharging the chemical waste in a large amount, because the process is wet.
In contrast, heat-developable photosensitive materials capable of performing the heat treatment the development process have been developed and are put to practical use.
Heat-developable photosensitive material is made of a laminate of photosensitive silver layer that consists of from salt of fatty acids, organic reducing agent, small amounts of silver halide dispersed in a binder resin, and support plate such as a paper or plastic film or metal foil or glass plate.
On the other hand, polymethyl methacrylate resins and polyvinylacetal resins, cellulose acetate resins, polyvinyl acetate resins, cellulose acetate propionate resin, cellulose acetate butyrate and polyvinyl butyral resin, having excellent film forming properties are the used for the photosensitive layers of the heat developable photosensitive material. Among them, a polyvinyl acetal resin is used as the best.
These binder resins are generally used in a solvent casting method.
The resin is dissolved in a solvent such as MEK and acetone, alcohol, toluene having relatively low boiling point, and cast onto a support, and dried. This is described in many references.
The improvement of productivity of the film forming is required on the solvent casting method as described above. Reducing the time to the step of release of formed film from the step of resin solution casting onto a support is important. However, the phenomenon of skinning occurs in the process of drying the resin solution, to get the resin film. Skinning is a phenomenon that the casting film surface is solidified by drying, and the skin prevents the evaporation of solvent of inside. That occurs significantly when we use low-boiling temperature solvents.
When the skinning occurs, the problem that the image characteristics are deteriorated, because the silver particle density is lowered, had occurred.
For example, Patent Document 1 discloses a technique of preventing skinning to improve coating properties, the skinning layer is prevented from formation by using a solvent of poor solvent for the binder.
However, a new problem arose that the dispersibility of the silver particles becomes extremely worse when the poor solvent is used in the silver halide light-sensitive material.
Further, in Patent Document 2, a method of combining the three processes has been disclosed.
The method comprises the steps of first, casting the resin solution onto a support, second, applying the vacuum pressure to the support to enable the casting film to adhere to the support, and third, feeding the anti-skinning solution to the outlet of the resin solution.
This is possible to prevent the adhesion to the film or the scattering of anti-skinning solution, this method can suppress the skinning. However, there is a problem that adhesion between the support and the casting film becomes worse in this method.